The invention relates to material unloading devices and methods and, more particularly, to portable devices for use in unloading bulk materials from a railcar.
As used herein, bulk materials include aggregate, crushed stone, grains, sand, plastic pellets or other relatively free-flowing material that may be shipped in bulk by rail or bottom dump trucks. In situations where a relatively large amount of bulk material is required at a location at one time, for example for a large construction project, the amounts needed are, from a practical standpoint, too large to utilize trucks. In these situations, the use of railcars for transportation of the bulk material is necessary, as transportation of bulk material by railcar is significantly less expensive than by truck. However, once the bulk material has been transported to the desired site, it must still be unloaded from the railcars in an effective, cost-efficient manner.
The predominant type of railcar used for transporting bulk materials such as aggregate is an open top bottom dump hopper car, constructed of steel. Because these cars are emptied by dumping from the bottom, expensive permanent facilities are typically required beneath the railroad tracks to receive the dumped bulk materials. Typically, these facilities include large, rail-supporting I beams mounted in thick, high-strength concrete foundations cast in place beneath the railroad tracks. A steel hopper, sized to span the entire length of the railcar, is permanently installed beneath the beams. Vibratory feeders are generally required to center the unloaded bulk material from the hopper on one conveyor by which the unloaded bulk material is carried to a stockpile for later use.
These permanent unloading facilities generally take several months to install and are very expensive to build. Once built, such facilities are never moved, and typically only the hopper can be salvaged. The concrete foundation can only be abandoned or destroyed. Thus, these unloading facilities have been left in place once the site is no longer used for unloading bulk materials and are either left idle or demolished and reclaimed. The old, abandoned facilities can pose a hazard to the general public from a safety standpoint.
As an alternative to the permanent unloading facility, there has also been some use of conveyors designed to fit between the track and the railcar. However, the capacity of such systems is limited by the space constraints and the use of such systems is labor intensive since the conveyors must be moved in and out from beneath each of the gates of the railcar to be unloaded.
Thus, there is a need for an improved method of unloading bulk materials from railcars that utilizes a device that is relatively fast and inexpensive to install, and which is reusable.